This is an application from the Department of Medicine, Divisions of Nephrology and Hematology, and the Department of Surgery at the Duke University Medical Center to participate as a clinical center in the NIH- sponsored Hemodialysis Vascular Access Clinical Trials Consortium. The proposed trial is a randomized prospective evaluation of a series of novel agents such as (Elmiron(R) pentosan polsulfonate sodium see appendix A, or Tissue Factor Pathway Inhibitor TFPI see appendix A or other novel interventional agent) versus placebo in the prevention of hemodialysis vascular access stenosis and thrombosis in hemodialysis AV access. Patients will be randomized to therapy with Elmiron(R) (or other trial agent) versus placebo. Randomization criteria will include whether this is a first or a subsequent AV graft as well as graft location and the presence or absence of diabetes mellitus. All patients entering the study will be screened with AV access flow, determined by the ultrasound dilution technique. Grafts with initial flows less than 1000 ml/min will not be randomized. Patients will be prospectively followed with monthly measurements of hemodialysis vascular access flow by ultrasound dilution. Decrements in AV access flow greater than 25% will prompt evaluation by venography. The primary end point in the study will be the development of a greater than 50% stenosis as determined by biplanar venography when associated with a concurrent flow decrement. All episodes of Access thrombosis will also serve as primary endpoints. Secondary end points will include all other AV access complications and hospitalizations. Ancillary studies will include response of AV access to intervention, access patency, and the cost of the placebo and intervention arms of the study.